The present disclosure generally relates to electronic displays, and specifically to calibrating brightness and colors in such electronic displays.
An electronic display includes pixels that display a portion of an image by emitting one or more wavelengths of light from various sub-pixels. Responsive to a uniform input, the electronic display should have uniform luminance. However, during the manufacturing process, various factors cause non-uniformities in luminance of pixels and sub-pixels. For example, variations in flatness of a carrier substrate, variations in a lithography light source, temperature variations across the substrate, or mask defects may result in the electronic display having transistors with non-uniform emission characteristics. As a result, different sub-pixels driven with the same voltage and current will emit different intensities of light (also referred to as brightness). In another example, “Mura” artifact or other permanent artifact causes static or time-dependent non-uniformity distortion in the electronic display, due to undesirable electrical variations (e.g., differential bias voltage or voltage perturbation). Variations that are a function of position on the electronic display cause different display regions of the electronic display to have different luminance. If these errors systematically affect sub-pixels of one color more than sub-pixels of another color, then the electronic display has non-uniform color balance as well. These spatial non-uniformities of brightness and colors decrease image quality and limit applications of the electronic displays. For example, virtual reality (VR) systems typically include an electronic display that presents virtual reality images. These spatial non-uniformities reduce user experience and immersion in a VR environment.